1. Field of the Invention
This invention relates to a numerically controlled device (NC device) such as a numerically controlled slitter device (NC slitter) for automatically cutting a sheet material such as paper or the like in a desired slitter width.
2. Description of the Prior Art
An NC slitter of this type has a plurality of slitting knife units, in which intervals between the slitting knife units are numerically controlled to desired values by moving the respective slitting knife units. As an example of a conventional NC slitter, there is an NC slitter in which slitting knife units are moved by driving motors provided at the respective slitting knife units. As another example, there is an NC slitter in which a screw provided through a plurality of slitting knife units is driven by one driving motor to move the respective slitting knife units.
Among the conventional examples described above, the NC slitter in which the driving motors are provided at the respective slitting knife units is convenient in that the slitting knife units can be moved simultaneously in both rightward and leftward directions by driving the respective driving motors in desired rotating directions, but its structure in which one driving motor is provided at each of the slitting knife units is complicated and high in cost, and its wirings and controls are also complicated.
The other NC slitter in which the screw and the one driving motor are employed is simple in structure as compared with the above-described former example, but the slitting knife units cannot be simultaneously moved in rightward and leftward directions. In other words, the slitting knife units can be simulataneously moved rightward or leftward, but if one slitting knife unit is desired to be moved in the rightward and the other slitting knife unit is desired to be moved in the leftward direction, both the slitting knife units cannot be simultaneously moved in the desired directions. For example, the slitting knife unit to be desired to be moved in the rightward direction must be first moved, and then the slitting knife unit to be desired to be moved in the opposite leftward direction must be moved. Thus, the more the number of the slitting knife units is increased, the longer it takes to complete the movements of the respective slitting knife units to the respective desired positions.
An object of the present invention is to provide an NC device which can eliminate the problems of the above-described conventional prior art and can simultaneously move a plurality of slitting knife units in both rightward and leftward directions and which has a simple structure.